Means for launching projectiles



April 1964 R. G. STRICKLAND ETAL, 3,129,636

MEANS FOR LAUNCHING PROJECTILES Filed Sept, 28, 1960 RICHARD G. STRICKLAND ARTHUR J. WENNERSTRO M I NV EN TORS BY THOMAS J. HOLDEN DONALD M. .SANDLER AT TORNE Y5 United States Patent M 3,129,636 MEANS FOR LAUNCHING PRGJECTHPES Richard G. Strickland, Stewartstown, Pa, and Arthur J.

Wennerstrom, Zurich, Switzerland, assignors to Aircraft Armaments, 1nd, Coekeysville, Md, 2 corporation of Maryland Filed Sept. 28, 1960, Ser. No. 539,014 3 Claims. (Cl. 89-17) This invention relates to ordnance, and more particularly, to recoilless launching systems.

In a system of the class described, propellent gases created by the burning of a propellant in the combustion chamber of such system react on a projectile to accelerate the same along the gun tube in one direction while a portion of such gases expand through a balancing nozzle in the opposite direction. With proper design, the momentum of the expanding gases balances the momentum of the projectile such that recoil of the gun is eliminated.

The pressure in the combustion chamber peaks rapidly upon ignition of the propellent whereby an extremely large pressure gradient across the balancing nozzle is produced in a very short time interval. Such gradient produces high velocity gases of great turbulence that erode the burning charge and carry away a significant portion of unburned charge through the nozzle. Not only is this wasteful, but the amount of charge that is actually burned will vary from shot to shot causing a considerable variation in the muzzle velocity of the projectiies.

To secure uniformity in muzzle velocities, it is essential that the discharge of unburned propellant through the balancing nozzle be reduced to a minimum. Those skilled in the art have, in the past, resorted to the insertion of a frangible disc in the throat of the nozzle. The use of such disc permits the pressure in the combustion chamber to build up to a value somewhat greater than that attainable without the disc, and also prevents the initial discharge of unburned propellant. However, rupture of the disc occurs prior to complete combustion of the propellant with the result that considerable propellent loss accompanies blow-out of the disc.

It is therefore an object of this invention to reduce propellant loss through the balancing nozzle of a system of the class described by preventing unblocking of the nozzle until combustion of the propellant is substantially complete. As a feature of this invention whereby the object thereof is achieved, a nozzle blocking plug is rigidly attached to the base of the projectile by means of a boom extending through the propellant charge so that the plug and projectile move as a unit} At the instant of propellant ignition, the rigid plug induces a rapid pressure rise in the combustion chamber which serves to increase the propellant burning rate. The propellant gases so created react on the projectile to accelerate the same in one direction along the gun tube. Initial displacement of the projectile in the one direction causes withdrawal of the plug in the one direction until the nozzle is unblocked whereupon the propellent gases expand through the nozzle in the opposite direction. Since the momentum is initially low when the projectile begins its initial displacement, very little reaction is imparted to the gun when the rigid nozzle block is used.

The more important features of this invention have thus been outlined rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will also form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure 3,129,636 Patented Apr. 21, 1964 is based may readily be utilized as a basis for designing other structures for carrying out the several purposes of this invention. It is important, therefore, that the claims to be granted herein shall be of sufficient breadth to prevent the appropriation of this invention by those skilled in the art.

The drawing shows a cross-section of a recoilless launching system with the projectile configuration in position prior to ignition.

A recoilless launching system incorporating the present invention is indicated generally at 10. System 19 includes gun 11 having combustion chamber housing 12 with gun tube 13 attached at one end and balancing nozzle 14 attached at the other end. Housing 12 has chamber 15 which is preferably enlarged relative to bore 16 of tube 13 although the exact shape is not important so far as this invention is concerned. Housing 12 has opening 17 connecting chamber 15 to bore 16. Nozzle 14 has restriction 18 coaxially located in alignment with the axis of tube 16 to define a throat through which propellant gases in chamber 15 can expand.

Projectile configuration 20 has, at one end, nose portion 21 which fits within bore 16 of tube 13. At the other end of configuration 20 is nozzle block or plug 22. Boom 23 rigidly attached to the base of nose portion 21 and to plug 22 interconnects the plug to the nose portion so that they move as a unit relative to the gun. Propellant charge 24 is arranged in cylindrical shape and surrounds boom 23, it being held in place by screening 25. When nose portion 21 is inserted in bore 16 of tube 13, configuration 20 is supported in the gun with plug 22 substantially filling throat 18 and boom 23 surrounded by charge 24 is in chamber 15.

In describing plug 22 as substantially filling throat 18, the intended meaning is that plug 22 fits within the throat. The exact percent of the throat that is blocked by the plug may be determined experimentally. With a given gun design, a given peak pressure in the combustion chamber is permissible. With a charge sufficient to produce the desired muzzle velocity, the peak chamber pressure may exceed the permissible pressure when the throat is completely blocked. All that is necessary is to decrease the blocked area of the throat until the desired peak pressure is no longer exceeded. From experiments, it has been found that desirable results are attained when the blocked area is from 50% to 70% of the throat area.

Plug 22 preferably extends beyond throat 18 into the portion of the nozzle wherein expansion of the gases takes place. The maximum distance is determined by the amount of gun recoil that can be tolerated. Since plug 22 effectively prevents nozzle 14 from counteracting the reaction of the projectile configuration until the plug is Withdrawn, the nozzle should be blocked only when the velocity of the configuration is low since the momentum associated therewith is small. However, the nozzle need be blocked only until combustion is substantially completed. The rapid pressure rise associated with the blocked nozzle increases the burning rate so that the length of plug 22 can be small.

In operation, ignition lead 26 is energized setting off charge 24 and producing propellent gases internal to chamber 15. Because nozzle 14 is blocked, there is a rapid build-up of pressure in the chamber accompanied by almost complete combustion of the charge. The high pressure gases react upon the rear face of nose portion 21 and upon plug 22. Since plug 22 is non-frangible and of a smaller cross-section that the nose portion, nozzle 14 remains blocked and a net force is exerted on the configuration which moves the same forward through the gun tube. Plug 22 also moves forward against the action of the gases since plug 22 is rigidly connected to nose portion 21. After predetermined movement of the projectile configuration in the forward direction, plug 22 is withdrawn from the throat 18 of the nozzle. When this occurs, the propellent gases expand through throat 18 to provide a thrust on the gun which balances the thrust on the gun due to movement of the projectile configuration.

Those skilled in the art will now appreciate that the use of a non-frangible nozzle plug that is rigidly connected to the nose portion of the projectile permits complete combustion to occur prior to unblocking of the balancing nozzle. It should be noted that while the drawing shows plug 22 as being enlarged relative to boom 23, it is possible to utilize the boom, itself, as the nozzle plug.

What is claimed is:

1. The combination with a recoilless gun having a tubular barrel, a combustion chamber attached to the barrel, and a balancing nozzle attached to the combustion chamher, said nozzle having a restriction defining a throat smaller in cross-section than said combustion chamber, of a projectile configuration for use with said gun, said configuration comprising a main body portion, said portion having an axial boom attached thereto, said cnfiguration being inserted in the gun with the body portion supported by the barrel when the boom is in the combustion chamber, a propelling charge surrounding said boom, ignition of said propelling charge causing the same to produce propellent gases in the combustion chamber which propel the body and boom along the barrel in one direction, a portion of said gases expanding through the throat of said nozzle in the opposite direction whereby the forces acting on the gun in both directions are substantially equal and there is no recoil, and a rigid plug on the free end of said boom, said plug substantially blocking said throat before ignition of said charge and being nonfrangible against the effects of propellent gases produced after ignition so that said body, boom and plug are movable along said barrel as a unit in said one direction in response to said gases, said plug serving to prevent substantial gas flow through said throat only until after predetermined movement of said unit in said one direction.

2. For use with a gun having a combustion chamber, a balancing nozzle on one end of the chamber and a gun .tube on the other end of the chamber, said nozzle having an orifice defining a throat that is smaller in cross-section than said combustion chamber: a projectile configuration comprising a nose portion at one end of a size to slidably fit said gun tube and a plug portion at the other end of substantially the same size as said orifice, said projectile configuration adapted to be inserted in the gun with the nose portion supported in the tube and the plug portion substantially filling said orifice whereby said projectile configuration closes said combustion chamber, and means for producing propellent gases internal to said chamber whereby said projectile configuration is caused to move through said tube in one direction, said plug being of non-frangible material and movable through said orifice in said one direction upon movement of said configuration in said one direction, said orifice remaining blocked by said plug to substantially prevent the flow of said gases through said orifice only until after predetermined movement of said projectile in said one direction causes said plug to be withdrawn from the orifice in said one direction whereby the propellent gases can then expand therethrough to provide a thrust which counterbalances the thrust of the moving projectile.

3. The combination with a gun having a combustion chamber, a balancing nozzle at one end of said chamber and a gun tube at the other end, said nozzle having an orifice defining a throat that is smaller in cross-section than said combustion chamber, of a projectile configuration comprising: a nose portion at one end of said configuration slidably engaged in said gun tube, means for producing propellent gases in said chamber that act on said nose portion to propel the same away from the nozzle, 2. non-frangible plug impervious to said propellent gases blocking said orifice, and means responsive to predetermined displacement of said nose portion away from said nozzle for moving said plug out of said orifice thereby unblocking the same.

References Cited in the file of this patent UNITED STATES PATENTS 2,490,101 Staver Dec. 6, 1949 2,671,401 Abramson Mar. 9, 1954 2,924,149 Musser Feb. 9, 1960 

1. THE COMBINATION WITH A RECOILLESS GUN HAVING A TUBULAR BARREL, A COMBUSTION CHAMBER ATTACHED TO THE BARREL, AND A BALANCING NOZZLE ATTACHED TO THE COMBUSTION CHAMBER, SAID NOZZLE HAVING A RESTRICTION DEFINING A THROAT SMALLER IN CROSS-SECTION THAN SAID COMBUSTION CHAMBER, OF A PROJECTILE CONFIGURATION FOR USE WITH SAID GUN, SAID CONFIGURATION COMPRISING A MAIN BODY PORTION, SAID PORTION HAVING AN AXIAL BOOM ATTACHED THERETO, SAID CONFIGURATION BEING INSERTED IN THE GUN WITH THE BODY PORTION SUPPORTED BY THE BARREL WHEN THE BOOM IS IN THE COMBUSTION CHAMBER, A PROPELLING CHARGE SURROUNDING SAID BOOM, IGNITION OF SAID PROPELLING CHARGE CAUSING THE SAME TO PRODUCE PROPELLENT GASES IN THE COMBUSTION CHAMBER WHICH PROPEL THE BODY AND BOOM ALONG THE BARREL IN ONE DIRECTION, A PORTION OF SAID GASES EXPANDING THROUGH THE THROAT OF SAID NOZZLE IN THE OPPOSITE DIRECTION WHEREBY THE FORCES ACTING ON THE GUN IN BOTH DIRECTIONS ARE SUBSTANTIALLY EQUAL AND THERE IS NO RECOIL, AND A RIGID PLUG ON THE FREE END OF SAID BOOM, SAID PLUG SUBSTANTIALLY BLOCKING SAID THROAT BEFORE IGNITION OF SAID CHARGE AND BEING NONFRANGIBLE AGAINST THE EFFECTS OF PROPELLENT GASES PRODUCED AFTER IGNITION SO THAT SAID BODY, BOOM AND PLUG ARE MOVABLE ALONG SAID BARREL AS A UNIT IN SAID ONE DIRECTION IN RESPONSE TO SAID GASES, SAID PLUG SERVING TO PREVENT SUBSTANTIAL GAS FLOW THROUGH SAID THROAT ONLY UNTIL AFTER PREDETERMINED MOVEMENT OF SAID UNIT IN SAID ON DIRECTION. 